Sperm size evolution in African greenbuls (Passeriformes: Pycnonotidae)

Sperm morphology is highly diversified across the animal kingdom and recent comparative evidence from passerine birds suggests that postcopulatory sexual selection is a significant driver of sperm evolution. In the present study, we describe sperm size variation among 20 species of African greenbuls...

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Bibliographic Details
Published in:Biological journal of the Linnean Society 2016-02, Vol.117 (2), p.337-349
Main Authors: Omotoriogun, Taiwo C, Albrecht, Tomas, Hořák, David, Laskemoen, Terje, Ottosson, Ulf, Rowe, Melissah, Sedláček, Ondřej, Lifjeld, Jan T
Format: Article
Language:English
Subjects:
Animal behavior
birds
competition
diversification
Evolution
evolutionary rate
Genetic drift
interspecific variation
Passeriformes
paternity
phylogenetic signal
phylogeny
Pycnonotidae
sexual selection
Sperm
sperm competition
spermatozoa
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Summary:Sperm morphology is highly diversified across the animal kingdom and recent comparative evidence from passerine birds suggests that postcopulatory sexual selection is a significant driver of sperm evolution. In the present study, we describe sperm size variation among 20 species of African greenbuls and one bulbul (Passeriformes: Pycnonotidae) and analyze the evolutionary differentiation of sperm size within a phylogenetic framework. We found significant interspecific variation in sperm size; with some genera exhibiting relatively long sperm (e.g. Eurillas) and others exhibiting short sperm head lengths (e.g. Phyllastrephus). However, our results suggest that contemporary levels of sperm competition are unlikely to explain sperm diversification within this clade: the coefficients of inter‐male variation (CVbₘ) in sperm length were generally high, suggesting relatively low and homogeneous rates of extra‐pair paternity. Finally, in a comparison of six evolutionary or tree transformation models, we found support for both the Kappa (evolutionary change primarily at nodes) and Lambda (lineage‐specific evolutionary rates along branches) models in the evolutionary trajectories of sperm size among species. We therefore conclude that African greenbuls have more variable rates of sperm size evolution than expected from a neutral model of genetic drift. Understanding the evolutionary dynamics of sperm diversification remains a future challenge.
ISSN:0024-4066
1095-8312
DOI:10.1111/bij.12663